According to the state of the art of amorphous silicon technology, integrated line drivers are of the high output impedance type so as to limit the transistor stress and therefore the drift in the threshold voltage of these transistors. With this type of driver, when lines are not selected (which is the case during more than 99% of the display addressing time) they are in a so-called floating state. In this state, the lines are sensitive to all parasite variations and particularly variations related to capacitive couplings due to intersection of lines and columns. More precisely, for each new selected line, the data to be displayed is applied on all columns of the display: as a result of capacitive couplings due to intersection between lines and columns, the voltage levels of unselected lines vary on these columns. This has an effect on the display quality of the display.
In particular, these couplings can lead to unwanted selection of a line on the display and as a result data on this line may be modified. This is the so-called multi-line selection problem.
Other unwanted effects can occur depending on the method used to make the storage capacitor associated with each pixel electrode of the active matrix. In particular, when this storage capacitor is made using the pixel row selection line, these couplings will also cause variations in voltage levels stored on pixels through the storage capacitor. The display quality is affected.
Moreover, in such a structure, the total capacitance of each line depends on the video information displayed on the pixels in this line through the storage capacitor. This total capacitance depends on the sum of all coupling capacitances between this line and each column in the matrix, plus the sum of all storage capacitances in series with the associated liquid crystal capacitances made with this line, as a first approximation. This dependence may introduce display nonuniformities.